Proper insulation is one of the fundamental design considerations in any electrical component. In a multiwinding magnetic component, such as a transformer, proper insulation must be provided between the various windings and between the windings and the magnetic core. Further consideration must be given to providing proper insulation protection to certain critical winding locations such as winding terminations. Not only is such insulation essential to insure proper functioning of the component and any associated circuitry and to provide personal safety, but in most applications of use the component must meet specific Government or Safety Agency promulgated performance and construction requirements.
The insulation system of a small transformer for office machinery typically achieves these requirements by using insulated windings combined with a multiple turn insulating tape wrapping positioned between different windings to achieve several layers of insulation and by using multiple wire sleevings at the terminal ends of the windings. This particular construction insures that multiple layers of insulation, as may be required by government or safety agency requirements, will always appear between the primary and secondary windings. Since coating, spraying, potting and painting of insulation on the wires does not normally meet such agency promulgated safety requirements, the insulation must always comprise a layered film of insulation with the required number of layers between windings being specified differently in different jurisdiction but most often being normally three layers.
These required tape wrapping and sleeving operations constitute a substantial portion of the overall cost of the transformer. Furthermore the complexity of the insulation construction results in a reduction of production yields of acceptable transformers thereby further increasing their cost.